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Particles, Volume 3, Issue 4 (December 2020) – 5 articles

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Open AccessArticle
Constraints on CP-Odd ALP Couplings from EDM Limits of Fermions
Particles 2020, 3(4), 719-728; https://0-doi-org.brum.beds.ac.uk/10.3390/particles3040047 - 16 Dec 2020
Viewed by 480
Abstract
We discuss constraints on soft CP-violating couplings of axion-like particles with photon and fermions by using data on electric dipole moments of standard model particles. In particular, for the axion-like particle (ALP) leptophilic scenario, we derive bounds on CP-odd ALP-photon-photon coupling from data [...] Read more.
We discuss constraints on soft CP-violating couplings of axion-like particles with photon and fermions by using data on electric dipole moments of standard model particles. In particular, for the axion-like particle (ALP) leptophilic scenario, we derive bounds on CP-odd ALP-photon-photon coupling from data of the ACME collaboration on electron EDM. We also discuss prospects of the storage ring experiment to constrain the ALP–photon–photon coupling from data on proton EDM for the simplified hadrophilic interactions of ALP. The resulting constraints from experimental bounds on the muon and neutron EDMs are weak. We set constraint on the CP-odd ALP coupling with electron and derive bounds on combinations of coupling constants, which involve soft CP-violating terms. Full article
(This article belongs to the collection Dark Matter and New Physics of Hidden Particles)
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Open AccessArticle
Spin Susceptibility in Neutron Matter from Quantum Monte Carlo Calculations
Particles 2020, 3(4), 706-718; https://0-doi-org.brum.beds.ac.uk/10.3390/particles3040046 - 26 Nov 2020
Viewed by 473
Abstract
The spin susceptibility in pure neutron matter is computed from auxiliary field diffusion Monte Carlo calculations over a wide range of densities. The calculations are performed for different spin asymmetries, while using twist-averaged boundary conditions to reduce finite-size effects. The employed nuclear interactions [...] Read more.
The spin susceptibility in pure neutron matter is computed from auxiliary field diffusion Monte Carlo calculations over a wide range of densities. The calculations are performed for different spin asymmetries, while using twist-averaged boundary conditions to reduce finite-size effects. The employed nuclear interactions include both the phenomenological Argonne AV8′ + UIX potential and local interactions that are derived from chiral effective field theory up to next-to-next-to-leading order. Full article
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Open AccessArticle
Neutron Star Cooling Within the Equation of State With Induced Surface Tension
Particles 2020, 3(4), 693-705; https://0-doi-org.brum.beds.ac.uk/10.3390/particles3040045 - 21 Nov 2020
Cited by 1 | Viewed by 485
Abstract
We study the thermal evolution of neutron stars described within the equation of state with induced surface tension (IST) that reproduces properties of normal nuclear matter, fulfills the proton flow constraint, provides a high-quality description of hadron multiplicities created during the nuclear-nuclear collision [...] Read more.
We study the thermal evolution of neutron stars described within the equation of state with induced surface tension (IST) that reproduces properties of normal nuclear matter, fulfills the proton flow constraint, provides a high-quality description of hadron multiplicities created during the nuclear-nuclear collision experiments, and it is equally compatible with the constraints from astrophysical observations and the GW170817 event. The model features strong direct Urca processes for the stars above 1.91M. The IST equation of state shows very good agreement with the available cooling data, even without introducing nuclear pairing. We also analysed the effect of the singlet proton/neutron and triplet neutron pairing on the cooling of neutron stars of different mass. We show that the description of the compact object in the center of the Cassiopeia A does not necessarily require an inclusion of neutron superfluidity and/or proton superconductivity. Our results indicate that data of Cassiopeia A can be adequately well reproduced by a 1.66M star with an atmosphere of light elements. Moreover, the IST EoS reproduces each of the observational datasets for the surface temperature of Cassiopeia A either by a rapidly cooling ∼1.955M star with paired and unpaired matter or by a 1.91M star with the inclusion of neutron and proton pairings in the singlet channel. Full article
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Open AccessFeature PaperArticle
Direct Photons from Hot Quark Matter in Renormalized Finite-Time-Path QED
Particles 2020, 3(4), 676-692; https://0-doi-org.brum.beds.ac.uk/10.3390/particles3040044 - 20 Oct 2020
Viewed by 500
Abstract
Within the finite-time-path out-of-equilibrium quantum field theory (QFT), we calculate direct photon emission from early stages of heavy ion collisions, from a narrow window, in which uncertainty relations are still important and they provide a new mechanism for production of photons. The basic [...] Read more.
Within the finite-time-path out-of-equilibrium quantum field theory (QFT), we calculate direct photon emission from early stages of heavy ion collisions, from a narrow window, in which uncertainty relations are still important and they provide a new mechanism for production of photons. The basic difference with respect to earlier calculations, leading to diverging results, is that we use renormalized QED of quarks and photons. Our result is a finite contribution that is consistent with uncertainty relations. Full article
(This article belongs to the collection High Energy Physics)
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Open AccessArticle
Equation of State of Strongly Magnetized Matter with Hyperons and Δ-Resonances
Particles 2020, 3(4), 660-675; https://0-doi-org.brum.beds.ac.uk/10.3390/particles3040043 - 13 Oct 2020
Cited by 1 | Viewed by 579
Abstract
We construct a new equation of state for the baryonic matter under an intense magnetic field within the framework of covariant density functional theory. The composition of matter includes hyperons as well as Δ-resonances. The extension of the nucleonic functional to the [...] Read more.
We construct a new equation of state for the baryonic matter under an intense magnetic field within the framework of covariant density functional theory. The composition of matter includes hyperons as well as Δ-resonances. The extension of the nucleonic functional to the hypernuclear sector is constrained by the experimental data on Λ and Ξ-hypernuclei. We find that the equation of state stiffens with the inclusion of the magnetic field, which increases the maximum mass of neutron star compared to the non-magnetic case. In addition, the strangeness fraction in the matter is enhanced. Several observables, like the Dirac effective mass, particle abundances, etc. show typical oscillatory behavior as a function of the magnetic field and/or density which is traced back to the occupation pattern of Landau levels. Full article
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